Process for the production of nitric oxids in internal-combustion engines.



' t in driving internal combustion engines, 1t 1s UNITED STATES PATENT OFFICE.

armour muw or snnzsnnticxnn, GERMANY, nssronon 'ro nnnnsnmv a snnrmn, onsmmsonsr'r mrr snsonnzmxrms HAFTUNG, or sunnnocxnn, GERMANY.

PROCESS FOR THE PRODUCTION OF NITRIC OXIDS IN INTERNAL-COMBUSTION ENGINES.

80 Drawing.

To all whom it may concern.-

lh' it known that I, lluoom' Dnmrn, a sub ject of the Emperor of Germany, and residing at Snarbriicken, in the Empire of Gernmny, have invented certain new and useful Improvements in Processes for the Production of Nitric Oxid in Internal-Combustion Engines, of which the following is a 9?}(2Cifi0l1i3l01'l t is generally known that at high tom peratures and high pressures, the nitrogen and the oxygen in the atmosphere unite to form a chemical compound, 2'. 0., nitric oxid; and, it has been proposed to ignite a mixture of air and gas in it closed combustion space to produce this compound. The importance of avoiding decomposition of the nit rie oxid so formed has also llt'tll recognized, and it has lit-1'1! proposed to employ, for this aurposv. u (jliit'li fall of the pressure, as wel as of the trmpcratnrc. Attempts have been made to utilize, for the combustion space under picssul'v. the cylinders of internal eoinl'instion cllginrs, in order to make use of the work produced by the increase of pres" sure which take place tin-rein. But no irnetieally useful result has been obtained, ecunsr the internal unnbustion engines, as ordinarily t'olmirlictcd, proved unsuitable for the reqnirenu-nts of tho illPl'lIIU Clltllllit'lll process in question.

Experiments have shown that the waste gasesof the ordinary combustion engine conloin either no nitric oxid at a l, or else contain only small traces of it, 1 no reason being that the engine is constructedncoordim to the requirements of a thermically usefiii generation of power, which necessarily ini'olves a high compression, at great. excess of air, and as low a temperature as possible during the cycle.

The advantages of low temperatures for ihcrmic efliciencv are consequences, first, of the increase of t e specific heat, and second, of the rapid growth of the cooling water losses at; rising temperatures; Accordingly advisable to employ mixtures wlthbut a,

' small'proportion of gas, but to compress such mixtures as highly as possible; and,

further, toobtainas low temperatures as P i l hroughout the entire cycle f erations. w,

On the other hand, if the internal combustlon engme 1s tobc used essentially for Patented Oct. 29, 1918.

the production of nitric oxid, the carrying out of this thermo-chcmical process renders necessary a complete deviation from the thcoreticnl requirements of the thermo-mechanical process as described above. Instead of the preliminary conditions for thermic efficiency, the preliminary conditions for chemical ciliciency must first of all be paid attention to, the two types of internul COIYIbllSilOI'l engines having in common only the requirement that the internal combnstion engine which shall work economically with the chemical process shall be dcsigned to produce power.

For the chem ical process are required: as high temperatures as possible; their duration for a definite time which, preferably, should be equal to the time necessary for the formation of nitric oxid; and, in addition to the highest temperature, as re )id as possible a fall of temperature in or or to limit the decomposition of the nitric oxid formed.

sary, therefore, to develop another and more iqiproprinte mode of operation; and it is the (1)100!) of the present invention to provide nn improved method or process, in order to effect the desired production of the nitric oxid in the engine, of which the most important feature is the utilization of the maximum umount of either the physical or the chemical heat of the working mixture or of both, irrespective, however, of the addition of oxygen as practically required for the formation oxygen of the nitric oxid.

The gaseous contents of the cylinder consist of the combustible mixture and of the excess of air as necessary for the formation of the nitric oxid; but instead of air, or as substitute for a part of it, oxygen may be by heating the mixture, either before or after its entrance into the cylinder. The maximum temperature with respect to the chemical heat is obtained by means of mix tures havin r as reat a calorific effect as possiblc, and, a so, by means of a high temperature at the end of the coi'npression period, viz. nearly up to the point where self-ignition takes place, the limit being reached when the engine works with sclfdgnition.

The physical heat is preferably obtained by utilizin for pro-ha ing the mixture, that heat w iich otherwise would be lost; and for that purpose the heat passin through the cylinder walls and thus into tie cooling water may be used, as well as the heat of the wihaust gases. In the first case, it is suflieicnt to cool the cylinder to a less extent, or even not to cool it at all, but in some cases heating of the compression space also, for instance by means of the exhaust gases, may prove advantageous.

Utilizing the exhaust gases for the preheating is preferably effected in heat-ex' change a 'iparatus; but th addition of heat, to the mixture may also be brought about by retaining a part of the hot exhaust gases within the cylinder, in which, it is advisable that the highest possible exhaust temperatures should be obtained in order to reduce the amount of spent gases used to a mini mum, such toimiperatures being produced either y lessening the cooling of the cylinder, or by throttling the exhaust port, that is to say, by changing the exhaust pressure or tension. A still further method of increasing the amount of physical heat of the mixture, consists in injecting appropriate quantities of highly-heated gas, air, or steam into the mixture during compression.

In order to increase the amount of chemical heat in proportion to the volume, it is im portant to remove from the cylinder the exiaust gases remaining therein, and to replace them by an appropriate quantit of fresh mixture, which may be effected by scavengin with either cold or hot air, the former being advantageous in that the temperature of the cylinder wall is reduced, with the result that the possibilit of a pre liminary explosion is diminished while at the same time, the temperature at the end of the compression may be correspondingly higher. The amount of the chemical heat ofthe mixture may also be increased by the addition either of oxygen to the air used for the mixture, or of vaporized or atomized oil, or its equivalent, to the gas if a poor as must be employed; and its increase may ikewise be effected by conducting the com bustible mixture under pressure into the cylinder.

The higher temperatures of the thermochemical process necessitate greater losses of heat to the cooling water than are met with in the thcrmo nechanical process heretofore in use; but these losses are diminished it the combustion pressure is kept low, because the giving off of heat of the mixture increases with. the pressure. In order, however, to obtain the high temperature required for the formation of the nitric oxid, via, tcmperic tures that are chauwtcrizcd by the increased pressure at the dead point, tic compression space must be so large that at least a three fold increase of pressure may be effected by the combustion. 0n the other hand, the combustion space will become too large, and the expansion curve, in consequence, too flat, if the combustion pressure is to be kept low, while the mixture is subjected to very/high heat, so that by reason of the diminution of the losses to the cooling water, a high teih perature is obtained, the losses being in creased in such event by reason of the decom position of the nitric oxid formed. This, however, may be obviated by commencing compression below atmospheric pressure, whereby the compression space may be smaller but the temperature at the end of the compression may be kept at the desired hci ht. The same effect may be also obtained by (coping the inlet valve open after the dead point is reached, and during a. portion of the compression stroke, so that part of the mixture is not compressed.

For a successful utilization of the heat, it is neccssar that combustion be completed when the ighesttemperature is reached. A perfect, suddenly-finished combustion eutai s highest temperatures and aquiclr fall of the same; it facilitates the formation of the nitric oxid and limits its decomposition; and it may be attained by a thorough mixing of the gas and the air, the mixing becoming more perfect if the articles of the mixture are forcibly whirle through one another, for instance if a part of the mixturc,i. 0., gas or air or even steam in a heated state he ilr jected into the other part. The pro-heating of the mixture is valuable also with respect to quick and complete combustion, because a good mixture pro-heated up to the point of self-ignition will burn immediately after ignition. commences down to and into even the most remote corners of the combustion space, and in a perfectly uniform manner.

Considering the time of formation of the nitric oxid, which depends upon the temperatures attained, the expedients above doseribcd will be employed either sing y or in certain appropriate combinations, as may appear practical in view of. the kind of gas employed, the number of revoFutions of the en -ne, or other conditions.

11 the case of high-speed engines, it may happen that the times for the formation of the nitric oxid, at normal working conditions, are too short; and in such a case it is advisable to increase the length of the time during which the temperature has the height necessary for the formation of the nitric oxid by introducing mixture parts of high calorific effect after ignition has taken place, 2'. 6., in the manner carried out in the uniform pressure process. This procedure is likewise especially advantageous in connection with slow-speed engines if, in consequence of the application of nor gases, very high temperatures cannot e attained and thus the times for the formation of the nitric oxid become rather long.

The fall of temperature necessary, after the formation of the nitric oxid, to diminish its decomposition, may be accelerated by the addition of special spaces to the cylinder, which are brought into communication with the interior 0 the cylinder just at the proper moment, and into which the gas quickly expands, thus producing a Sudden fall of pressure which entails the fall of temperature required. The same result may also be obtained by subjecting the mixture, during expansion, to the action of a cold jet of air or gas, which thoroughly whirls the particles of the mixture about, so that the transfer of heat to the cylinder wall is accelerated and all particles of the mixture are brought in contact with the heat-absorb ing inner surfaces of the same.

I claim as my invention 1. The herein-described method of producing nitric oxid in internal combustion engines, which consists in preheating the combustible mixture, together with an excess of gaseous fluid to form the nitric oxid, by means of the exhaust gases, in order to increase the amount of heat of the mixture in proportion to its volume; maintaining the high temperature of the mixture up to the end of the compression period, to effect the formation of the nitric oxid, combustion being completed when the highest tempcrature is reached; and effecting a rapid all of temperature immediately thereafter, to diminish the decomposition of the nitric oxid fermed'.

a, The herein=deScribed method of produc ng nitric oxid in internal combustion engines, which consists in preheating the combustible mixture, together with an excess of gaseous fluid to form the nitric oxid, by means of the exhaust gases, in order to increase the amount of heat of the mixture in proportion to its volume; maintaining said exhaust gases at a maximum temperature; maintaining the high tcm cratare of the mixture up to the end of tie compression period, to eflect the formation of the nitric oxid, combustion being completed when the highest temperature is reached; and effecting a rapid fall of temperature immediately thereafter, to diminish the dccomposition of the nitric oxid formed.

3. The herein-described method of producing nitric oxid in internal combustion engines, which consists in injecting a highly-heated, gaseous fluid into the com; bustible mixture, to thoroughly mix to gcther the particles of the mixture, and to increase the heat of the latter in proportion toitsvolume;maintainingthehigh tom erature of the mixture up to the end oi the compression period, to cfl'cct the formation of the nitric oxid, combustion being co'mpletrd when the highest tom )erature is reached; and effecting a ra )id all of term peratureimmediatelytherea ter,to diminish the decomposition of the nitric oxid formed.

In testimony whereof I allix my signature in presence of two witnesses.

RUDOLF DRAW l). 

